Self-expanding mandrel.



J. E. BERGSTRD'M.

SELF EXPANDING MANDREL.

APPLICATION FILED MAY 20, 1908.

. 1 005 92 Patented Oct. 17, 1911.

Inventor: 11.13.13 argscrtim. v4 QM. W by Attn rnag 3,

JOHAN ERIK BERGSTRUM, OF CI-IBIQvTIANIA, NORWAY.

SELF-EXPANDING MANIDREL.

Specification of Letters Patent.

Application filed May 20, 1908.

Patented Oct. 17, 1911. Serial-No. 433,951.

To all whom it may concern:

Be it known that I, JOHAN ERIK BERG- sTRo'M, manufacturer, citizen of the Kingdom of Norway, and residing at Trondhjemsveien 113/113", Christiania, Norway, have invented a new and useful Improvement in Self-Expanding Mandrels, which invention is fully set forth in the following specification.

For securing pulleys, sleeves, rings or similar working-pieces to be turned in lathes or otherwise worked it has been the practice to use a conical mandrel, upon which the pulley, etc., is threaded and held fast by the mandrel quoining itself into the hole arranged in the central portion of the working-piece. There is thus obtained, however, only an imperfect fastening, which also often results in the piece being clamped obliquely upon the mandrel.

My present invention has for its object to provide a mandrel which may be termed a self-expanding mandrel and which is provided with an easily expansible sleeve cylindrical exteriorly so that the said sleeve can be brought into intimate engagement with the inner surface of the central hole of the working piece. In this manner is obtained a safe and efficient fastening of the piece, which at the same time may be easily loosened.

My invention is illustrated in the accompanying drawing, in which Figures 1 and 2 are views in longitudinal section and front elevation respectively of the mandrel with sleeve and a ring clamped upon the latter. Figs. 3 and 4 are cross sectional views showing the mandrel and the sleeve in two modified forms.

The outer cam surface of the actuating member -2 of the mandrel 1 formsin section one or more curves 3, the generating point of which describes an Archimedian spiral.

The cam member -2 is surrounded by a sleeve 5 which is split at 4; and the inner surface of which is curved in accordance with the above mentioned curves. The sleeve has an outer cylindrical surface and is preferably provided with a plurality of longitudinal grooves -9- which increase the yieldability of the sleeve.

Then a ring 6 is to be fastened to a mandrel a sleeve is used the cylindrical portion of which latter has a diameter slightly larger than that of the central hole of the which project into recesses 7 in the collar 8- of the sleeve is rotated in the clockwise direction (Fig. 2), whereby the sleeve on account of the shape of the surfaces sliding against each other is gradually and uniformly expanded so that the whole periphery of the sleeve finally will engage the walls of the ring. The ring is thereby securely clamped to the mandrel and constantly remains completely centered, as the curved surfaces of mandrel and sleeve correspond exactly with each other.

In Fig. 1 is shown a single curve 3. However, it is understood that exactly the same effect is obtained when two, three or more such curves (Figs. 2 and 3) are used. Besides the curves or engaging surfaces in the sleeve need not be complete, but they may be interrupted by grooves 10 so that in the sleeve inner engaging projections l1 are formed as shown in Fig. 3. It is seen that the sleeve will remain centered in all positions of the mandrel.

In order that the sleeve 5 may be more easily slid off from the mandrel the active portion 2 of the latter is preferably made slightly tapered the sleeve being provided with a correspondingly conical inner surface, while the outer surface of the sleeve remains cylindrical.

When securing working-pieces with conical holes a sleeve is used whose outer surface is, of course, correspondingly tapered.

Having now described my invention what I claim as new and desire to secure by Letters Patent is 1. In a self-expanding mandrel, a mandrel proper having one or more eccentric faces forming in all cross-sections on the mandrel Archimedian spiral lines, in combination with a resilient holding sleeve constituting a single piece having an interior eccentric face corresponding to that of the mandrel proper and provided eXteriorly with a cylindrical surface, said sleeve having longitudinal grooves for increasing its resiliency.

2. In a self-expanding mandrel, a mandrel proper having one or more eccentric faces forming in all cross-sections on the mandrel Archimedian spiral lines, in combination with a resilient holding sleeve constituting a single piece split on one side and having an interior eccentric face corresponding to that of the mandrel proper and provided eXteriorly With a cylindrical surface, said sleeve having longitudinal grooves for increasing its resiliency and being adapted to be sprung into the opening of the Work.

3. In a self-expanding mandrel, a mandrel proper being slightly tapered and having one or more eccentric faces forming in all cross sections on the mandrel Archimedian spiral lines, in combination With a resilient holding sleeve constituting a single piece split on one side and having an interior eccentric face corresponding to that of the mandrel proper and provided exteriorly With a cylindrical surface, said sleeve having longitudinal grooves for increasing its resiliency and being adapted to be sprung into the opening of the Work.

In testimony whereof I have signed this specification in the presence of tWo subscribing Witnesses.

J OHAN ERIK BERGSTRGM.

lVitnesses:

AXEL LAHN, RICHARD STOKKE.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

